ohhhhh...but we dnt knw if it passes through j or not so maybe it has a j value
consider the whole set up on the
consider an arbitrary vector and the unit vector
We assume both vectors are parallel.
Lets assume the arbitrary vector is
+
Gradient of
= Gradient of the other vector
Thus if an arbitrary
vector and
are parallel, the co-effecient of j for the arbitrary vector has to equal 0.